Large-sized umbrellas, such as beach umbrella, are well known. A conventional large-sized umbrella is shown in FIGS. 1 and 2 of the attached drawings, comprising a shank 10 to which a wire-winding device 11 operable by a crank arm 15 is fixed for winding/unwinding a wire 12 extending through the shank 10. The wires 12 moves a runner 13 along the shank 10 for driving a plurality of rib-stretcher sets 14 to open the umbrella (FIG. 1) or to close the umbrella (FIG. 2).
The conventional wire-winding device, however, has disadvantages. For example, the conventional wire-winding device comprises no means to automatically stop the operation thereof when the umbrella is fully opened. Thus, over-tensioning the wire may occur in the neglect of a user. This may eventually cause a damage or even break of the wire.
Furthermore, the conventional wire-winding device does not comprise means to maintain a half-opened condition of the umbrella. Thus, if the user fails to properly secure the wire at the fully open position, the umbrella automatically close itself due to gravity and may cause damage to the user. A known way to solve the problem is to add a latch to the wire-winding device that prevents the crank arm from being rotated. However, the latch complicates the structure of the umbrella wire-winding device and requires a tedious operation. Manufacture costs of the umbrella are also increased.
It is thus desirable to have an umbrella wire-winding device that overcomes the above problems.